Gary,

I get the best results with two identical hot ends. If you're trying to mix and match, you can probably make it work, but you're making it harder on yourself. I find that the same filament needs different settings in different hot ends--even temperature. ABS that prints great at 245C in a 3mm Hexagon may need 255C in a 1.75mm E3Dv6 to get the same layer adhesion.

I guess the real question is what you're trying to accomplish. If you want to play with a 3D printer, by all means buy whatever strikes your fancy and have fun tuning and trying. If you want to make things with a 3D printer, I recommend getting a matched pair of genuine E3Dv6 hot ends in 1.75mm and climbing the learning curve once.

As far as adjustment, I get as close to 1:1 filament movement as practical with the E-Steps setting in the Marlin firmware and then tune from there based on how the prints are turning out. I don't typically tune in the slicer. I just dial the E-Steps up and down with the printer control panel. If the top is a little overfilled, I turn it down. If it's got gaps, I turn it up. If I have layer adhesion problems, I make sure that my extrusion width is at least 120% of the nozzle size, and then turn it up slightly or raise the temperature.

If you're using my hobbed bolts in a 4:1 drive extruder (all of the Itty Bitty extruders) I recommend starting at 615. My printers are all set between 600 and 625. The differences are probably just due to the tolerances on the 3mm and 1.75mm filament I have.

James

Quote Originally Posted by gddeen View Post
This test print is a little better...

2016-05-13 09.50.24.jpg
I find several type of 2 color dual extrusion objects. Side by side stuff (embedded) and overlapping.

I use two different types of nozzles, one very pointy and one flat.

Questions:
I set my steps per unit to 660... I find a flow rate of 80% in Cura (not from printer) works well.

- Should I remove nozzle, set to extrude 300mm, measure and repeat until it is exactly 300 mm?

Or, should I calculate 80% of the cross sectional area by length (volume) and use THAT as length?

- Different filaments PET-G, verses pure PLA, verses other PLA have different flow
rates at different temperature/pressure extrusions. Noticably so... I use flow rate
on the printer to correct (that affects RETRACTION!!!)

A) Is there a formulae for setting temperature / flow rate?

B) Does one switch to hardware retraction or just overkill it in cura so lowering the flow rate won't leave filament too close to the nozzle causing more ooze?

- Changing 660 steps per mm unit to 614 decreases or increases the amount of filament extruded?


Code:
// GDD // Explanations are here: http://reprap.org/wiki/Triffid_Hunte...ibration_Guide
    // GDD //----------------------------------------------------------My Settings ---------------------------------------------------------------------------------------
    // GDD // NEMA 17 with standard pitch M8 threaded rod:
    // GDD //(200 * 16) / 1.25 = 2560
    // GDD // NEMA 17 with SAE 5/16" threaded rod. It has 18 threads per inch (25.4mm / 18):
    // GDD //(200 16) / (25.4 / 18) = 2267.7165355
    // GDD // E-Steps: small_gear (motor) drives big_gear turns hob_bolt friction pushes filement.
    // GDD // e_steps_per_mm = (motor_steps_per_rev driver_microstep) (big_gear_teeth / small_gear_teeth) / (hob_effective_diameter pi)
    // GDD = (200steps/rev x 16microsteps) * (80teeth / 20teeth) / (6.325 mm * 3.14159) = 644.2
    // GDD James Clough (Manufacturer of hob gear & Itty Bitty Flex Extruder) suggests starting at 615


    // default settings

    #define DEFAULT_AXIS_STEPS_PER_UNIT   {80,80,2560,660.0}